The present invention relates generally to reciprocating compressor assemblies, and more particularly, to multi-stage compressors that have two or more cylinders.
Compressors are used in many cooling, heating or refrigeration systems to compress a refrigerant fluid which circulates through the system. In the case of reciprocating compressors, a motor or engine turns a crankshaft which actuates reciprocation of one or more pistons inside one or more cylinders. Low pressure refrigerant enters the compressor through an inlet port in the compressor's casing and may be housed temporarily in a reservoir defined by the casing. The low pressure refrigerant from the reservoir is then drawn into the cylinders through a passageway(s) and compressed by the piston(s) to a higher temperature and pressure. The high pressure refrigerant gas discharged from the cylinder(s) leaves the reciprocating compressor through an outlet port in the cylinder head or casing and flows to the other components of the cooling, heating or refrigeration system.
In a multi-stage reciprocating compressor, the refrigerant fluid discharged from one or more low stage cylinders is drawn through another passageway(s) to one or more high stage cylinders. The refrigerant gas is further compressed by the piston(s) in the high stage cylinders. By dividing the reciprocating compressor into stages, it is possible to more efficiently compress the refrigerant to a higher pressure than can be accomplished with a single stage reciprocating compressor.
As is typical with components in many mechanical systems, it is desirable to keep the size and weight of the compressor(s) in the heating or cooling system to a minimum while engineering the unit to provide the system with as much capacity and efficiency as possible. The passageways between the stages in many conventional multi-stage reciprocating compressors require tubing or piping external to the compressor to communicate the refrigerant between the stages of the compressor. Unfortunately, the external tubing or piping can be a source of vibration and high and low frequency noise. The external piping also increases the size and overall weight of the compressor. The external piping also creates extra joints which have the potential to leak and adds additional parts which necessitate additional manufacturing steps including the fitting of piping to the compressor casing.